Cooling fin



Jan. 12, 1937. R, C|||LTON 2,067,597

COLING FIN Filed May 22, 1935 v' INVENTOR.

"-/ Roza/m CHU, TON

A T'ORNE Y.

Patented Jan. 12, 1937 COOLING FIN Roland Chilton, Ridgewood, N. J., assigner to The Reed Propeller Co., Inc., a corporation of New York Application May 22, 1935, Serial No. 22,725

8 Claims.

This invention comprises an improved radiating fin means for use in heat interchangers in general, while a specific application to an aircooled engine cylinder barrel is illustrated in the drawing.

One object of the invention is to provide means for attaching iins of high conductivity material, such as aluminum alloy, to a member of high ,strength material, such as steel. Such light alloy iins cannot be attached to steel members by brazing or welding, and a further object of the invention is to provide an attaching means giving good thermal contact between the fins and the member to which they are secured.

Another object is to reduce the cost of finned cylinder construction by eliminating the machining time involved in the current practice of turning the multiple fins from a thick forging which involves a large poundage of scrap material.

A further object is to provide a finned construction applicable to a cylinder having flanges or other enlargements at each end. A still further object is to provide a replaceable finning means and to provide a plurality of similar, easily fabricated 1in units which may be assembled to produce a multi-finned organization for a cylinder.

Saving in weight and the ability to use closer iin spacing than is practicable with conventional methods are also included in the objects of the invention.

Other objects and advantages will be obvious from the following specification with reference to the drawing, in which:

Fig. 1 is a side view of an air-cooled cylinder barrel incorporating the fins of this invention;

Fig. 2 is a plan section through the barrel on the line 2-2 gf Fig. 1 showing a pair of n elements in separated relation;

Fig. 3 is a fragmentary section on the line 3 3 of Fig. 4;

Fig. 4 is a fragmentary section on the line 4 4 of Fig. l; and

Fig. 5 is a section through a 1in on the line K 5 5 of Fig. 2.

portion which is machined on the inner surface 22 to be a shrink fit at assembly over the cylinder barrel. The width of the base portion 2E? is such that each n contacts its neighbors on the sides of the base. Each fin is provided 5 with non-tapered end lugs 2li drilled with holes or eyes 2li to receive the long shear` pins 28, the thickness of the lugs Zll being half that of the base portions 2li. Thus, a set ofns may be assembled with the end lugs 24 in overlapping 10 relation and the eyes 25 in alignment.

The fin elements may be cheaply and rapidly fabricated by a ccining or cold forging operation from suitable stock whereby the dimensions may be held to close limits in quantity production. 15 in order to control the bore of the fin assemblage to give the desired shrink t over the barrel, a set of fins is preferably assembled on the shear pins 23 and supported on a suitable fixture for boring the inside diameter 22 to the desired fit. 20 One hinge pin is then removed and the fins brought up to desired shrink temperature whereupon the set is wrapped around the barrel and the second hinge pin is then driven through the overlapping eyes.

By this method it is practicable to maintain a high intensity of pressure between each fin base and the contacted barrel wall. When this intimate Contact is achieved the thermal drop across the joint becomes negligibly small. This desirable effect, coupled with the high conductivity material which may be med with the attachment methods of this invention, and further, the close nning spacing which may be economically used, gives a very much greater over-all cooling efliciency than can be obtained with integral steel ns which have lower conductivity, greater weight, and which are limited in height and spacing by manufacturing and conductivity limitations.

It should be mentioned that recent researches on the optimum iin proportions have demonstrated that high conductivity and much closer spacing and greater height than current practice, are desirable. As the output of air-cooled aircraft engines has been increased, limitations in the cooling capacity of the conventional fins have become of serious importance.

After the fins are assembled on the cylinder, the shrink fit of the fins will firmly hold the shear pins 2E in place. Assembly may be facilitated by providing bores 3i) in the cylinder hold-down flanges l2 through which the shear pins 28 may be passed to engage the iin eyes 25. This likewise will serve as a positive circumferential locator for the fins with respect to thecylinder.

It is known that older types of construction contemplated forming screw threads on the outside of the cylinder barrel and screwing thereon a iinned sleeve of different material. However, such a construction does not permit of closely spaced deep ns, and is much more expensive to manufacture.

While I have described my invention in detailf in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modications and changes.

What is claimed is:

1. The combination with a cylinder to be` cooled, of semi-circular rlns having end eyes assembled in overlapping relation, and secured around the cylinder by pins inserted through said eyes, the pin and eye axes being parallel to the cylinder axis, each said pin engaging more than two of said eyes. Y

2. The combination with a cylinder having exterior projections towards its ends, of iins comprising half rings assembled around the barrel with their ends in overlapping relation, and shear pins securing said fins by threading through holes in said overlapping ends, the pin and hole axes being parallel to the cylinder axis, and each said pin engaging the holes of more than two of said iins.

3. A stack of semi-circular fins having end eyes assembled in overlapping relation and secured by a pair of hinge pins to comprise a finned cylinder for encircling a cylindrical member.

4. Aniarticle of manufacture including a preformed semi-circular iin having an enlarged base izontactable with a cylinder, and a relatively thin iin portion terminating in thickened lugs each lug having an opening axially-parallel to the iin axis.

5. An article of manufacture including preformed semi-circular rin having an enlarged base contactable with a cylinder, and a relatively thin iin portion terminating in thickened lugs of a thickness equal to half the thickness of the enlarged base.

6. A nninglassemblage for a cylinder comprising a composite embracing cylinder composed cf an assemblage of semi-circular ns overlapping at their ends, and hinge pins engaging holes formed near the ends of said elements for securing said assemblage in shrink t relation about said cylinder.

'7. A composite air-cooled cylinder assembly comprising in combination a cylinder of material having a relatively low coecient of thermal expansion, a cooling n assembly comprising semi-cylindrical halves having hinge pin eyes at their ends, and hinge pins engaging said eyes and axially parallel to the cylinder, said halves being formed of material of relatively high coefficient of thermal expansion, said halves being organized, upon elevation in temperature thereof, for wrapping about said cylinder and for attachment to one another by insertion of said hinge' pins in the eyes of said cylinder halves and for attachment to said cylinder by shrinkageA due to cooling of said ns from the elevated temperature.-

8. A cooling fin assembly for embracement of a cylinder comprising finned half cylinders for tting engagement around said lcylinder, said Q half cylinders having, at the end elements thereof, coacting perorate lugs, and hinge pins engaging said perforate lugs for holding said half cylinders in assembled relation around said' cylinder.

ROLAND CHILTON. 

